TDD (Time Division Duplex)

Time Division Duplex uses one frequency band for both uplink and downlink, alternating between them in time. TDD is the dominant duplexing scheme for 5G mid-band (3.5 GHz), most Wi-Fi, and many enterprise small-cell deployments, because it can flexibly allocate capacity between directions and avoids the need for paired spectrum.

Categories: Radio Access NetworkSignalingSecurity Controls

TDD in context

The radio access network is the layer where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations, downgrade attacks and jamming, and defenses hinge on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

Signaling protocols carry the control-plane instructions that set up calls, register subscribers, hand over sessions and route SMS. SS7, Diameter, GTP-C and SIP are the four dominant families, and interconnect exposure of any of them is treated by GSMA FS.11 / FS.19 / FS.20 as a top-tier telecom risk.

To place TDD in the wider telecom-security picture, review Lawful Interception, F1 Interface, Xn Interface, RADIUS, TCP and TCAP.

Related terms

Related topic hubs

  • Diameter Attacks S6a IDR/PUR/CLR abuse, subscriber tracking, LTE signaling attacks.
  • SS7 Security SS7/MAP/CAP/SCCP attacks and defenses across 2G/3G interconnect.
  • Diameter Security 4G/LTE Diameter threats across IPX/roaming and DEA defenses.
  • Signaling Firewall Unified SS7/Diameter/GTP/SMS signaling firewall framework.

More from the TelcoSec Glossary

Browse the full TelcoSec Glossary, the Ultimate Guide to Mobile Network Security, or the P1 Arsenal of telecom-security tools.